1. Field of the Invention
This invention relates to improvements in manually operated fluid dispensing devices and is concerned, particularly, with features of construction that reduce the manufacturing cost, simplify the valving, and that facilitate assembly and inspection.
2. Description of the Prior Art
Many different forms of manually operated fluid dispensing devices have been proposed in the prior art for dispensing a wide variety of fluid products. One form disclosed in U.S. Pat. No. 3,061,202, granted Oct. 30, 1962 utilizes a spring return piston and cylinder pump with spring biased inlet and outlet check valves. Such an arrangement, in general, is complex, having many parts and is relatively costly to manufacture, assemble and inspect.
Other forms of dispensing devices, as disclosed in U.S. Pat. No. 3,986,644, granted Oct. 19, 1976, and U.S. Pat. No. 3,995,774, granted Dec. 7, 1976, employ a deformable bulb to define the pump chamber, the inlet and outlet valves comprising flap valves formed in a flange provided on the deformable bulb. A valve housing is closed by a cover plate that is firmly secured in sealing relation against the flange. Pressure in the valve housing, however, produces stresses in the plate that tend to cause leakage problems and valve interference, particularly in respect of the outlet valve that seals against the plate. Additionally, while such dispensing devices utilize but few parts, expensive and hard to obtain materials are required for the deformable bulb. As a result the manufacturing cost is high.
A copending application for patent of John R. Cary and Walter H. Wesner bearing Ser. No. 754,056, filed Dec. 23, 1976, now abandoned, said application being a continuation of their application Ser. No. 626,812, filed Oct. 29, 1975, now abandoned, discloses a form of fluid dispensing device in which the pump chamber is defined by a bellows pump having a closed end, an open end, and a sidewall having multiple flexible sections, and embodying in a single part, the functions of a piston, a fluid chamber, a return spring, and a valve. Since the bellows pump is molded from inexpensive and readily obtained plastic materials, a significant reduction in manufacturing cost is obtained. Other features of the device, and in particular, the valving arrangement leave something to be desired from the standpoint of assembly and inspection.
Thus, there still exists a need for further improvements in manually operated fluid dispensing devices, particularly in respect of a construction that simplifies the valving, the number of parts required, their manufacturing cost, and their handling, and additionally, the cost of assembly and inspection of the assembled devices.